Electromagnetic device



July 3, 1962 l. w. cox

ELECTROMAGNETIC DEVICE 2 Sheets-Sheet 1 Filed April 14, 1958 July 3, l1962 l. w. cox

ELECTROMAGNETIC DEVICE 2 Sheets-Sheet 2 Filed April 14, 1958 II l lll I@ III United States Patent O 3,042,842 ELECTROMAGNETIC DEVICE Irvin W. Cox', West Allis, Wis., assignor to Cutler-Hammer, Inc., Milwaukee, Wis., a corporation of Delaware Filed Apr. 14,1958, Ser. No. 728,285 11 Claims. (CL 317-185) This invention relates to electromagnetic devices and more particularly to electromagnetic operators of the fluid-damped type.

While not limited thereto, the invention is especially applicable to alternating current electromagnetic devices for operating contacts and the like.

To decrease undesirable variations in magnetic attraction due to the cyclic variations of the alternating current and thereby to decrease the noise, ithas been the usual practice to provide alternating current electromagnetic devices with a phase shifting shading coil. Such shading coil is not only a wattage consuming device, particularly at higher frequencies, but also overheats the pole faces, increases the rate of wear and necessitates the use of more conductor material such as copper to conduct the increased holding current. High speed magnets have the inherent disadvantage that the repeated high-shock armature impacts against the pole faces of the laminated core cause mushrooming and wear, misalignment and noise. This is transmitted, sometimes resonantly, to the contacts to significantly affect the electrical life thereof.

It has been proposed to damp an alternating current electromagnetic device by means of a dashpot or to partially immerse the same in oil. However, it has been found that these devices do not provide critical damping, that is, damping suiiicient to arrest resonance, nor do they render the electromagnetic device quiet in operation.

Accordingly, a general object of the invention is to provide and improved electromagnetic device which overcomes the aforementioned disadvantages to a significant degree.

A more specific object of the invention is to provide an improved electromagnetic device of the Huid-damped type which affords critical damping thereof.

Another specific object of the invention is to provide an improved alternating current electromagnetic operator wherein a plurality of magnetic forces are applied to the armature symmetrically around a central axis and iiuid damping is symmetrically applied to the armature over a large area.

A further specific object of the invention is to provide an improved alternating current electromagnetic operator which is exceptionally quiet in operation and has a markedly longer mechanical life.

Another object of the invention is to provide an alternating current electromagnetic device having reduced weight and power consumption compared to its work 'capacity and which can be readily and economically con- .structed.

Further objects and advantages of the invention will hereinafter appear.

While the apparatus hereinafter described is effectively adapted to fulfill the objects stated, it is to be understood that I do not intend to confine my invention to the particular preferred embodiment of electromagnetic device disclosed, inasmuch as it is susceptible of various modifications without departing from the scope of the appended claims.

The invention will now be described with reference to the accompanying drawings, wherein FGURE l is a top view of the electromagnetic device vconstructed in accordance with the invention;

' FIG. 2 is a sectional View taken along lines 2--2 of FIG. l;

A 3,642,842 Patented July 3, 1962 ice FIG. 3 is a partly sectional view taken along lines 3-3 of FIG. l; and

FIG. 4 is a sectional view taken along lines 4-4 oi FIG. 3.

lReferring to FlGS. 2 and 3 of the drawings, there is shown an electromagnetic device having a generally cupshaped housing member l provided with an internal, sub

' stantially semi-spherical depression 12 centrally of its bottom portion and an internal annular groove 14- around the rim of its open end. A generally cup-shaped supporting member 16 having an exteriorly stepped, circular depending outer wall '17 is partially telescoped into housing member l0 to close the open end of the latter. ln this position the rim of housing member 10` abuts against shoulder 18 of the supporting member and the two members are sealed to one another by a resilient O-ring 19 accommodated in annular groove 14. Supporting member 16 is additionally provided with a central bore 2i) and a tubular inner wall 22 surrounding the bore and depending into the interior of the housing member. Supporting member 16 is further provided with two pairs of angular spaced, reamed apertures 24, also shown in FIG. l, around the periphery of the upper llat portion thereof for providing terminal connections as hereinafter described. Supporting member 16 may have symmetricaily interposed between holes 24 angularly spaced and internally threaded holes 26, shown in FIG. 1, extending part way into supporting member 16 for securing a contact structure or the like to the upper portion of the device.

A cylindrical electromagnet having a laminated core 28 with an axial bore 30 and provided with a plurality of angularly spaced, depending pole pieces 32, more clearly `Seen in FIG. 4, and a coil 34 surrounding each pole piece is rigidly embedded in suitable plastic or thermosetting material 36 such as epoxy in the annular space between outer wall 17 and inner wall 22 of supporting member 16. Inserts 38, each having a tapped hole 40 extending part way therein from the outside, are'accornmodated in apertures 24 and surrounded by plastic material 36 for securing the same to and insulating the same from supporting member 16. Inserts 38 are provided with a frusto-conical iiange flaring outwardly at their outer ends and substantially complimentary to the reamed portions of apertures 24 to prevent insertion thereof cornpletely through the latter. The inner ends of inserts 38 are provided with a peripherally knurled flange 42 to rigidly secure the same from rotation in the plastic material Vand an annular grove 44 to facilitate connection of coils 34 thereto. The ends of the coil wires may be wrapped around grooves 44 and soldered therein to form an electrical connection. Suitable external electrical terminals may be threaded into tapped holes 40.

A cylindrical, laminated armature 46 having an axial bore 48 corresponding to and coaxial with bore 30 of core 28 is mounted for reciprocatory movement in the space between the electromagnet and the bottom portion of housing member 10 within the housing member. Armature 46 is embedded in a frame 50 of plastic or thermo-Setting material such as epoxy with its annular sealing surface 5'2 exposed to the free end faces of pole pieces 32.

A generally inverted cup-shaped member 54 is provided with a pair of peripherally knurled flanges 56 l,and embedded thereby co-axial-ly in plastic frame member 50. Member 54 is provided with a central aperture 58 having a form complimentary to 'a partial sphere. An actuator rod `60 having Ia spherical end portion 62 is secured to member 54 by insertionI of the rod through aperture 58 `to the extent that spherical end portion 62 engages the complimentary pontion of aperture 5S. A disc-shaped respace42 taining member 6d having a substantially semi-spherical depression 66 centrally thereof `for accommodating the remainder of spherical end portion 62 is inserted in cupshaped member d and the rim of the latter is for ed inwardly to secure the parts together. The restricted portion of aperture 5S may be a predetermined 'amount larger in diameter than rod 6@ adjacent such restricted portion to alford a limited amount of movement of spherical end portion '52 in its supporting structure.

A generally inverted cup-shaped member 68 is provided with an .axial `aperture through its closed end for accommodating rod 6i). An armature return spring 7 t) surrounds r-od ntl within cup-shaped member 68 and is compressed between members 54 and 63 to return the armature to its normal position when `the electromagnet is deenergized. Member 63 is provided adjacent its upper closed end with an annular groove 72 for receiving yan internal circular bead 74 on the large end of a gener-ally conical, flexible diaphragm 76. The small end of diaphragm 76 is reentnant inwardly of the diaphragm and is provided with an axial aperture surrounded by an integral vbead 7S locked in a complimentary, `annular groove intermediate the ends of rod `el). Member 6&3 is accommodated within the tubular inner wall 22 of supporting member lo and is provided at its rim with an annular flange 81 for abutment against the free end of such tubular inner wall. The large end of conical diaphragm 76 is compressed between member 63 and inner wall 22 to retain bead 74- in groove '72.

A bearing plate S2 having a central aperture 34 for accommodating rod 60 is secured by s-crews or the like to the upper surface of supporting member 16 to close bore 2l? from the atmosphere. The external end of rod 6o may be threaded for securing movable contacts or the like thereto.

The space within housing member 1t) surrounding the armature is completely filled with a predetermined quantity of damping fluid 37 such as oil or the like for controlling operation of the device. To contnol the effect of the damping fluid, armature frame is provided with a plurality of apertures 88 of predetermined sizes angular-ly spaced in the portion of armature frame Sil between armature lo and member 54. Damping fluid may also be provided within diaphragm '76 to Fill the space surrounding rod 6l) inasmuch .as the diaphragm operates with a constant volume, or some damping fluid 87 may enter this space along rod 6d ythrough the aperture in member 68,

Core 2S of the electromagnetic device is constructed by winding a ribbon-like strip of magnetic material onto an arbor to produce la cylindrical core having a plurality of spirally wound thin laminations and a bore axially there through. Portions of the strip are preferably cut out by an automatic notcbing machine as the strip is being wound to form pole pieces therebetween. The portions cut out may be of the same size but progressively spaced as the strip :is wound. The coils may be preformed and then inserted on the pole pieces. Inserts '38 are placed in apertures 24 and electrically connected to the coil wires. This subussembly is then placed within the generally annular space in supporting member 16 and thermo-setting potting material forced in the spaces therebetween to rigidly secure the magnet to the supporting member. The potting material also surrounds inserts 38 to rigidly secure the same to the supporting member.

Armature 46 and member 54 are molded in a frame d@ of thermo-setting material to form a rigid structure. Rod may then be inserted in aperture 53 and retaining disc 64 secured in place as hereinbefore described. ISpring 7 il, member 63 and diaphragm '76 may then be assembled on nod 6l) in the order named. Alternatively, rod 6b, disc 64, spring 70, member 68 and diaphragm 76 may be assemblcd on member 54 prior to molding of the latter and the armature in frame dll; The complete-d sub-assembly may then be fenced into bore Ztl tothe extent that flange tl abuts 4the free end of tubular inner wall 22. Bearing 4 plate 32 is secured to supporting member i6 to substantially seal the interior Iof the device.

Suitable damping fluid 87 is then placed in housing member lil, O-ring 19 placed in groove i4 and supporting member lo telescoped within housing member 19 into abutting engagement with shoulder 18 to complete the device.

While the armature is shown in FIGS. 2 and 3 in its closed or sealed position,4 spring '70' normally maintains the gaps between armature 46 and the pole faces open. Under Athis condition, damping uid 87 surrounds the armature and its frame 5t). When the coils .are energized, the magnet-ic forces in the gaps attract the armature upwardly. The damping fluid flows from the gaps .through apertures 88 and around `armature frame 5l), spring 70 is compressed and the armature seals into engagement with the pole faces. As a result, rod 66 moves upwardly to actuate contacts or Ithe like mounted on `the upper portion of supporting member 16. The cyclic variations of Athe alternating current which induce a Icorresponding y variable magnetic llux in the gaps would normally tend to vibrate the armature and impact the same against the pole faces as it approaches la sealed condition. The damping fluid absorbs such vibration to reduce noise and wear. As will be apparent from FIGS. 2 and 3, diaphragm 76 is provided with a configuration including a reentrant portion so that it operates with constant volume when the armature is actuated and, thus, may be completely lled with damping fluid. When the coils are deenergized, spring "70 returns the armature to its normally open position. As the armature starts to disengage the pole faces, the film of damping fluid on the sealing surfaces of these parts damps any vibration tending to be caused by the alternating magnetic llux, Ithus to prevent impact of the 'armature against the pole faces.

The damping fluid is maintained within the device by atmospheric pressure as well as by the enclosure. The loading to which the armature is subjected as by return spring 7 0 is less than that which would cause it tot oavitate and draw atmospheric Iair therein. This is for the reason that air might emulsify the damping fluid `that is, form compressible air bubbles in the damping fluid to deteriorate its damping characteristics. The actual loading is preferably set well below the cavitation loading to afford a safety factor.

An essential feature of the invention is the provision of a structure wherein the magnetic forces are symmetrically distributed around the central actuator rod 60 and large areas for contact with the damping fluid are provided by casting both the magnet and the armature in thermosetting material. Also, apertures 88 affording llow of damping fluid through armature iframe 50 are selected to provide optimum operating conditions atfording, along with the large surfaces critical damping as hereinbefore described. The improved `device aords the objects and advantageous results hereinbefore described through a wide range of operating frequencies. Thus, the low power consumption, the increased pole face life, low noise, and the increased life of all the moving parts are attainable whether the coil energizing Ifrequency under which it is operated is the commercial frequency of 60 cycles or a higher frequency in the range of 400 cycles and up.

I claim:

1. In an alternating current electromagnetic device, in combination, a housing having a cavity therein and being open at one end, `a laminated elctromagnet in one end of said cavity to close said open end and having a pole face, means surrounding said pole face to provide a relatively large surface area in the plane thereof, armature means having a relatively large surface area opposed to the surface area of said pole face, means mounting said armature means for reciprocatory movement in the other end of said cavity, actuator means connected to said armature means and extending to the exterior of said housing, and damping fluid completely filling and being confined in said other end of said cavity around said arma ture means.

2. The invention defined in claim 1, wherein said armature means comprises a laminated magnet armature member, a frame of thermosetting material having said armature member embedded therein with one surface of said armature member exposed for engagement with said pole face, said frame providing a relatively large surface area in the plane of said one surface, and at least one aperture in said frame affording a flow passage for said damping fluid.

3. The invention defined in claim 1, together with a bearing plate secured to said housing and having a restricted aperture for accommodating said actuator means t substantially close the interior of said housing from the atmosphere, resilient means normally biasing said armature means away from said pole face, energization of said electromagnet overcoming the force of said resilient means to attract said armature to said pole face, and said force of said resilient means being a predetermined amount less than the force which would cause said armature means to draw atmospheric air into said cavity whenv said electromagnet is deenergized.

4. The invention dened in claim 1, together with substantially conical resilient means connected between said actuator means and said housing for sealing said other end of said cavity from the atmosphere and to maintain the volume around said armature substantially constant when the latter is operated.

5. In a high frequency alternating current electromagnetic device, in combination, a separable housing having a cavity therein, an electromagnet having a pole face, thermosetting material embedding said electromagnet in one portion of said cavity with said pole face exposed, said thermosetting material providing a relatively large surface area in the plane of said pole face, an armature having a sealing surface opposed to said pole face and normally biased away from the rlatter and mounted for reciprocatory movement in another portion of said cavity,

a frame of thermosetting material having said armature embedded therein with said sealing surface exposed and providing -a relatively large surface area opposed Ato the first mentioned surface area, and damping fluid filling the space around said armature and said frame within said another portion of said cavity.

6. The invention dened in claim 5, wherein said housing comprises two substantially cup-shaped portions, the open end of one portion being telescoped within the open end of the other portion and having a shoulder for abutting against the rim of said other portion, said other portion having a groove adjacent its rim', and resilient means within said groove for sealing said portions to one another.

7. In an alternating current electromagnetic device, in combination, a generally cylindrical housing having a first portion and a second portion connected to one another, said rst portion having an axial bore surrounded by an inner tubular wall forming a substantially annular cavity therearound opening into said second portion, a cylindrical electromagnet having a plurality of angularly-spaced pole pieces and an operating coil surrounding each pole piece, said electromagnet being embedded in said annular cavity in thermosetting material with the pole faces exposed, said thermosetting material providing along with said pole faces a relatively large surface area in the plane of said pole faces, a cylindrical armature embedded in a frame of setting material with a surface of the armature exposed for sealing with said pole faces when said electromagnet is energized, said frame of thermosetting material providing along with said armature a relatively Ilarge surface area in the plane of said sealing surface, an actuating member connected to said armature frame and extending through said bore exteriorly of said housing, and damping fluid filling the space surrounding said armature and said frame within said second portion of said housing.

8. The invention defined in claim 7, together with a generally cup-shaped member Within said inner tubular wall having an annular flange at its rim for abutting against the free end of said inner tubular wall and an aperture in its closed end yfor accommodating said actuating mem-ber and an annular groove around its closed end, a substantially conical resilient diaphragm in said bore having a bead at its large end retained in said annular groove by. said tubular inner wall, and the small end of said diaphragm having a reentrant portion provided with an aperture surrounding and connected to said actuating member, said diaphragm sealing said cavity from the atmosphere.

9. The invention defined in claim 8, wherein said reentrant portion is of a lengthv to afford operation of said diaphragm at a substantially constant interior volume throughout the operating stroke of said actuating member.

l0. The invention defined in claim 9, together with a bearing plate having an aperture for guiding said actuating member secured to said iirst housing portion for closing said bore therein, and a ball and socket joint affording restricted pivotal movement of said armature on said actuating member.

1l. In an alternating current electromagnetic device, in combination, an alternating current electromagnet comprising a magnetic member and at least one energizing coil for energizing lsaid magnetic member, said magnetic member having a pole face forming one side of a gap, a magnetic armature member having a face forming the other side of said gap and being mounted for reciprocatory movement to close and open said gap, a housing for said electromagnet and said armature, means associated with said electromagnet providing with said pole face an enlarged damping surface area larger than the magnetically effective area of said pole face at said gap, means associated with said armature and movable therewith providing with said armature face an enlarged damping surface area larger than the magnetically effective face area of said armature at said gap, said enlarged surface areas being opposed to one another, and damping liquid within said housing maintaining said armature and said pole face and said means providing said enlarged damping surface areas completely immersed at all times, and said damping liquid cooperating with said enlarged surface areas to prevent armature vibration tending to be caused by the altenarting magnetic llux thereby eliminatv ing the use of shading coils and the like.

References Cited in the tile of this patent UNITED STATES PATENTS 1,761,759 Trombetta June 3, 1930 2,377,244 Kouyoumjian May 29, 1945 2,544,491 Davis Mar. 6, 1951 2,858,487 Immel Oct. 28, 1958 FOREIGN PATENTS 218,484 Germany Feb. 1, 1910 771,404 Great Britain Apr. 3, 1957 

